1. Field of the Invention
The present invention generally relates to a so called automatic station selecting and receiving apparatus, which automatically selects a broadcasting station according to so called "format information" on the basis of various information related to broadcasting stations (e.g. broadcast frequency information, broadcasting genre, broadcasting station name) stored in a memory in advance, and more particularly to an automatic updating operation of a current position of a movable body such as a car or vehicle to perform a format scanning operation.
2. Description of the Related Art
The number of FM (Frequency Modulation) broadcasting stations have increased nowadays, and the broadcast contents of the broadcasting stations are variegated. There exists a broadcasting station, which broadcasts only specific music (e.g. only Jazz, only Rock) for almost all of the broadcasting time of the day, and a broadcasting station, which has a major object to serve information such as news. In the U.S.A., where the number of broadcasting stations is very large, this variegation is even more promoted. This tendency of stations to broadcast only specific music or information is called a "format", and the information indicating this format corresponding to the broadcasting station is called "format information". Under this circumstance, there is a receiving system, which stores the format information with respect to each broadcasting station in advance, which determines the format information corresponding to the broadcasting station from the broadcast frequency etc. of the broadcasting station which electric wave is being received, and which supplies the users with the information. By use of this system, the user can selectively receive only the program from the broadcasting station or stations corresponding to the desired format (i.e. the desired tendency of programs). As for the receiving apparatus mounted on a movable body such as a car radio, since the condition of the broadcast electric wave which is being received varies from time to time, the station selection technique using this format information is important.
The receiving apparatus by use of the format information (which is referred to as an automatic station selecting and receiving apparatus, hereinbelow) stores the database related to the format information and the station name information in its internal memory. This database consists of a state file, a city file, a grid file, etc., which are regionally systemized. Here, the "grid" means a plurality of blocks, which are obtained by dividing the region in the vicinity of the receiving apparatus in a lattice like manner, and each of which has a constant area, for the sake of the receiving apparatus to efficiently perform the searching operation.
FIG. 3 shows one example of the construction of this grid.
In FIG. 3, the region in the vicinity of the receiving apparatus is divided into blocks in a lattice like manner, and a grid X is assumed to be a current grid (which means a grid in which the receiving apparatus is currently moving), and grids A to H around the grid X are grids in the region to which the receiving apparatus can access. The size of one grid is determined in accordance with the properties of the service area of the broadcasting station and the movable body (e.g. moving speed). For example, it is determined to be a 30 km square area.
In this type of automatic station selecting and receiving apparatus, the selection operation called a "format scanning operation" is performed. Namely, the receiving apparatus detects a broadcasting station or stations, from which the receiving apparatus can receive the electric wave, by seeking up or seeking down the receiving frequency on the basis of the format selected by the user. From the frequency information of the detected broadcasting station, the format information corresponding to this detected broadcasting station is read out from the memory. At this time, if the format specified by the user (for example, "Jazz" is specified as the format by the user) and the format information of the currently sought broadcasting station are not coincident with each other, the next broadcasting station will be sought. If they are coincident with each other, the seeking operation is ended, and the broadcasting station information is read out from the memory to be displayed on a display unit, and the receiving operation is continued by the frequency. The object region or area of this seeking operation may be limited within the current grid, or may be wider region than that.
In this type of automatic station selecting and receiving apparatus, the user uses an operation panel as shown in FIG. 4, to update the current grid in accordance with the movement of the movable body. By the operation of an operation panel 100 in FIG. 4, the region where the receiving apparatus recognizes the current position is determined and updated. After that, the station name information, the format information etc., can be accessed by the grid file in correspondence with the receiving frequency. For example, if the receiving condition is degraded as the automobile advances to the northeast direction, the user presses "N" and "E" keys on the operation panel 100 in FIG. 4, so that the current grid is updated to be the C grid in FIG. 3. The receiving apparatus sets the 9 grids with the C grid located at the center thereof as a next region (grid) to be accessed.
On the other hand, there is used a so called automatic format scanning (AFS) operation, in which the broadcast electric waves from the broadcasting stations having formats identical to each other are switched one after another to be received. In case that this automatic format scanning operation is performed by the specification of the user, the automatic format scanning operation is performed on an assumption that the position where the receiving apparatus is really positioned and the current grid set in the receiving apparatus are consistent with each other.
The above types of automatic station selecting and receiving apparatuses are disclosed in Japanese Patent Laid Open Nos. Hei.1-117,529 and Hei.2-238,723.
Furthermore, there is another type of automatic station selecting and receiving apparatus which performs the automatic grid updating operation to specify the current grid by use of the receiving condition and the data base.
However, in the above explained automatic grid updating or setting operation, since the movement of the movable body is not detected, the process to automatically updating or setting the grid is performed by the keying operation of the user. Namely, when the receiving apparatus gets away from the service area of the broadcasting station, which electric wave has been received by the receiving apparatus, in accordance with the movement of the automobile, there is raised such a problem that the user should specify the current position by operating the operation panel by himself to update the current grid.
More concretely, the user recognizes the degradation of the sounds as the noises are frequently mixed into the broadcasted sound or as the mute circuit of the FM receiving apparatus frequently operates, so that he is informed that the receiving condition of the broadcast which he is listening to is degraded. Thus, even if the receiving apparatus is an automatic station selecting and receiving apparatus which has the current position updating function to seek the current grid automatically, the updating operation of the current position should be performed by the user's operation after recognizing the degradation of the receiving condition by the virtue of the noise etc. Particularly, if the automobile on which the receiving apparatus is mounted is moving at a high speed on a highway, this updating operation should be performed quite frequently, which is quite troublesome and difficult for the user.
In case that the automobile is driven while the electric power of the receiving apparatus is turned off for a while, when the power of the receiving apparatus is turned on, there rises a case where the current grid setting and the actual position of the receiving apparatus are not consistent with each other. If the reception is continued as it is, since the electric wave of the pertinent broadcasting station which is the receiving object is very weak, the automatic format scanning operation cannot be normally executed, which is another serious problem.